The problem is occurring because the parameter value is not getting set to what you are probably expecting. Your "id" column in the table is an int datatype and that is what you need to pass it. See code below:
int comboBoxChoice = Convert.ToInt32(comboBox1.SelectedValue.ToString());
command.Parameters.AddWithValue("@id", comboBoxChoice);
Now provided your combo box is getting a value, this should do the trick.